Drying of layers of granular and other comminuted material



G. FLEISSNER Oct. 6, 1964 DRYING 0F LAYERS 0F GRANULAR AND OTHER COMMINUTED MATERIAL Filed July 10, 1959 2 .FIG.I.

INVENTOR GEROLD FLEISSNER ATTORNEY! United States Patent 3,151,955 DRYING 0F LAYERS 0F GRANULAR AND OTHER COMRHNUTED MATERIAL Gerolrl Fleissner, Egelsbach, Germany, assignor to Firma Fleissner & Co. G.m.b.H., Egeishach, Germany Filed July 10, 1959, Ser. No. 826,270 Claims priority, application Germany, July 11, 1958, F 26,149 3 Claims. (Cl. 34-164) The present invention relates generally to drying apparatus and, in particular, to a drying apparatus which is especially useful for drying granular material or layers of comminuted material.

It is an object of the present invention to provide means resulting in a very intensive drying action upon the material to be dried and especially upon intermediate layers of the material.

Another object of the present invention is to provide means resulting, in the case of superposed drying paths, in operation with a considerably reduced conveyor speed for the material to be dried and yet obtain the same results as with operation at a full conveyor speed.

It is another object of the present invention to provide means which insure the subdivision of one air stream into two or more streams or which concentrate several air streams onto one drying section.

A further object of the present invention is to provide means for attaining the directing of the air flowing over the conveying paths.

A still further object of the present invention is to assure the possibility of controlling the drying process according to the zones carrying material of different moisture content.

These and other objects of the invention will become further apparent from the following detailed description, reference being made to the accompanying drawings showing preferred embodiments of the invention.

In the drawings which illustrate the best modes presently contemplated for carrying out the invention:

FIG. 1 is a side view of a vibratory drier having three vibratory floors;

FIG. 2 is a cross section view of the drier of FIG. 1 and viewed along the section line 22; and,

FIG. 3 is a cross sectional View, similar to that shown in FIG. 2; but, showing an improved drier according to the present invention.

Briefly described, the present invention relates to a drying apparatus which is particularly useful to any granular material, the material being conveyed through the apparatus by a conventional vibratory system. Pursuant to an important aspect of the present invention, at least one means for conducting air and at least one means for circulating the air, or only the last mentioned means, are associated with the drying apparatus. The air circulation is controlled by one or both of said means in such manner that at least one air stream flows through or around the material. The material is supported on a suitably perforated means. Since the air passes through the material, a highly intensive drying action, including on intermediate layers of the material, is achieved. In prior art devices, the air is conducted only over and along the material which is to be dried so that only the surfaces of the material are subjected to the drying action. The present invention may be utilized in connection with conventional conveyors which, for example, may be tube vibrator systems, plate vibrators, tower vibrators, etc.

The counter-current principle is utilized wherever possible. The air is introduced at the material outlet of the drier and is conducted over heat radiators. A vent is provided at the material inlet of the drier to discharge as much air as is required by the drying process.

3,151,955 Patented @ct. 6, I964 "ice When using superposed drying paths, for example, three superposed floors, it is possible to operate the apparatus at one-third normal conveyor speed, for better drying action, and achieve the same output as with operation at normal or full conveyor speed. In general, the flow of material in superposed paths is directed downwardly, since conveyance thereof at the points of deflection is simpler than in the case where the material flows in the opposite direction.

The conveying paths are subdivided into various drying zones. At least one air stream is associated with each drying zone through the provision of a required number of fans. In lieu thereof, provision may be made for guide means to subdivide one air stream into two or more streams, said guide means also serving to concentrate several air streams onto one drying section. Each air stream is then conducted again over heating means.

For certain types of materials, best results are attained if the air current impinges vertically upon the material. In this connection there may be provided in the air flow path guide plates which extend in a vertical direction to direct the air. Such plates may extend into the ceiling space of the drier apparatus. Depending upon the material to be dried, similar means may be provided to direct the air stream, for example, obliquely into the material, the air flowing in the conveying direction or counter to it.

The drying process may be controlled according to zones having material of different moisture content by providing perforations of difierent size or number. For example, a rapid air flow may first be provided and at the end of the drying path an air stream of lesser volume or larger velocity may suflice. Accordingly, smaller perforations may be provided at the end of the drying path. However, it is generally desirable to attain a high air velocity. Consequently, it is necessary to utilize powerful fans or a large number of fans.

In order to prevent the air stream of one zone from entering the adjacent zone, imperforate plates may be used as support means or the perforations of perforated plates may be covered, allowing a predeterrrined distance from the perforated plate or conveying path. In this manner, while a passage of air is still efi'ected, it is stopped immediately below the conveying path.

Referring now to FIGS. 1 and 2 in detail, there is shown a housing of a vibratory drier 12, pursuant to the present invention, comprising a housing 14 in which there are mounted three vertically spaced superposed floors 1 which are arched to increase the strength thereof. Each floor is constituted by a vibratory screen member. The granular material M which is to be dried is introduced through a material inlet 16 into a funnel or bin 18, suitably mounted in the housing 14. A proportionating or rotary valve feeding device 20 is provided at the outlet of the funnel. As here shown, the device 29 comprises a pair of impellers which direct the material into one end of the uppermost vibratory screen member 1A along which it is conveyed, as indicated by arrow 22.

From the other end of the uppermost vibratory screen conveyor member, the material flows, as at M into the adjacent end of the intermediate vibratory screen coneyor member 13 along which it is conveyed, as shown by arrow 24, to the other end thereof. From said other end, the material flows, as at M into one end of the lowermost vibratory screen conveyor member 1C, along which it is conveyed, as shown by arrow 26, to the other end thereof from which it is fed to a pair of impellers 3 provided at the material discharge outlet 28 formed in the housing, being discharged therefrom, as shown at 3%). The impellers also serve as an air seal. It will be understood that the perforations in the screen members 1 are so dimensioned relative to the granular material M that the latter does not pass or fall therethrough.

perforations, as shown by arrows 32.

the ceiling 40 of housing 14 to downwardly directed deflectors'or guides 42 which direct the air vertically downwardly, as indicated at 32, through the materialon the three screen elements 1,'to the suction zone'4 from which the moist air is caused to recirculate through the heating means. It will be noted that the suction Zone 4 is large enough to provide ready access to the fans and to the elements 1 which can be removed or replaced therethrough.

Referring now to FIG. 3 in detail, there is shown another embodiment comprising a drier 12C having a housing 14C provided with four superposed screen floors 1A, 1B, 1C and 1D. Each floor is so mounted so that it is substantially parallel with the flow direction of an associated air stream, the entire air stream being heated by heating means 38 and being divided into four individual streams,'each of which flows through only one screen floor.

As here shown suitable air deflectors or guides 42 are provided to form a'first individual stream 44 which flows only through upper screen floor 1A, a second individual stream 46 which flows only through floor 113, a third individual stream 48 which flows only through floor 1C and a fourth individual stream 50 which flows only through bottom floor 1D.

Fan 34 is especially large or powerful to provide a large air flow, which is desirable for drying but the air pressure can be kept low since the air flow needs in every case to overcome the resistance of only one vibratory screen and the material thereon. Wide air shafts are provided on either side of the screens'to provide ready access to the individual screens. Fan 34, due to having a pair of opposed outlets, constitutes, in ellect, a pair of fan means.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed is new and desired to be secured by Letters Patent is:

1. Drying apparatus, for comminuted material, comprising: a housing including a material inlet and a material outlet; a plurality of vibratable screens mounted within said housing, each said screen being horizontally disposed, said screens being arranged in vertical superposed relationship, the material being received by the uppermost screen and conveyed horizontally, in succession, across each screen by vibration of said screens to the lowermost screen and then discharged from said housing through said outlet; one fan adapted for circulating a gaseous drying medium through said screens and the material thereon; a pluralityof bafile means, each screen being situated between two adjacent bafile means whereby each screen and the material thereon is dried by a separate stream of the circulating gaseous drying medium said separate streams derived from and combining into a single stream in said fan.

2. Drying apparatus, for comminuted material, comprising; a housing including a material inlet and a material outlet; a plurality of vibratable screens mounted within said housing, each said screen being horizontally disposed, said screens being arranged in'vertical superposed relationship, the material being received by the uppermost ,screen and conveyed horizontally, insuccession, across each screen by vibrationof said screens to thelowermost screen and then discharged from'said housing through said outlet; fan means adapted for circulating a gaseous drying medium through said screens and the material thereon; a plurality of battle means, each screen being situated between two adjacent baifie means whereby each screen and the material thereon is dried by a separate stream of the circulating gaseous medium, said fan means comprising one fan.

3. Drying apparatus, for comminuted material, comprising: a housingincludinga material inlet and a material outlet; a plurality of'vibratable screens mounted within said housing, each said screen being horizontallydisposed, said screens being arranged in vertical superposed relationship, the material being received by the uppermost screen and conveyed horizontally, in succession, across each screen by vibration of said screens to the lowermost screen and then discharged from said housing through said outlet; fan means adapted for circulating a gaseous drying medium through said screens and the material thereon; a plurality of bafiie means, each screen being situated between two adjacent baffie means whereby each screen and the material thereon is dried by a separate stream of the circulating gaseous drying medium; said plurality of screens comprising two pairs of screens, said fan means comprising one fan having two oppositely directed outlets, each'said fan outlet directing the gaseous medium to a different one of said pairs of screens.

References Cited in thefile of this patent v .UNITED STATES PATENTS 153,592 Mey July 28, 1874 446,759 Little Feb. 17, 1891 541,652 Blanchard June 25, 1895 2,050,477 Weisselberg Aug. 11, 1936 2,172,944 Norris Sept. 12, 1939 2,300,229 Knowles Oct. 27, 1942 2,301,249 Butterworth et al Nov.-10, 1942 2,365,769 Marshall Dec. 26,1944 2,758,388 Westerberg Aug. 14, 1956 2,797,498 Jipp July 2, 1957 3,012,331 Oholm etal Dec. 12, 1961 3,060,589 Wallin Oct. 30, 1962 FOREIGN PATENTS 1 868,107 France Dec. 18, 1941 849,968 Great Britain Sept.28, 1960 

1. DRYING APPARATUS, FOR COMMINUTED MATERIAL, COMPRISING: A HOUSING INCLUDING A MATERIAL INLET AND A MATERIAL OUTLET; A PLURALITY OF VIBRATABLE SCREENS MOUNTED WITHIN SAID HOUSING, EACH SAID SCREEN BENG HORIZONTALLY DISPOSED, SAID SCREENS BEING ARRANGED IN VERTICAL SUPERPOSED RELATIONSHIP, THE MATERIAL BEING RECEIVED BY THE UPPERMOST SCREEN AND CONVEYED HORIZONTALLY, IN SUCCESSION, ACROSS EACH SCREEN BY VIBRATION OF SAID SCREENS TO THE LOWERMOST SCREEN ADN THEN DISCHARGED FROM SAID HOUSING THROUGH SAID OUTLET; ONE FAN ADAPTED FOR CIRCULATING A GASEOUS DRYING MEDIUM THROUGH SAID SCREENS AND THE MATERIAL THEREON; A PLURALITY OF BAFFLE MEANS, EACH SCREEN BEING SITUATED BETWEEN TWO ADJACENT BAFFLE MEANS WHEREBY EACH SCREEN AND THE MATERIAL THEREON IS DRIED BY A SEPARATE STREAM OF THE CIRCULATING GASEOUS DRYING MEDIUM SAID SEPARATE STREAMS DERIVED FROM AND COMBINING INTO A SINGLE STREAM IN SAID FAN. 